The causes of type I and II diabetes are not yet clear, although both genetics and environment seem to be the factors. Type I is an autonomic immune disease and patient must take insulin to survive. Type II diabetes is more common form, is metabolic disorder resulting from the body's inability to make a sufficient amount of insulin or to properly use the insulin that is produced. Insulin secretion and insulin resistance are considered the major defects, however, the precise genetic factors involved in the mechanism remain unknown.
Patients with diabetes usually have one or more of the following defects:
    Less secretion of insulin by the pancreas;    Over production of glucose by the liver;    Independent of the glucose uptake by the skeletal muscles;    Defects in glucose transporters, desensitization of insulin receptors; and    Defects in the metabolic breakdown of polysaccharides.
Other than the parenteral or subcutaneous administration of insulin, there are four major classes of oral hypoglycemic agents used i.e sulfonylurea, biguanides, alpha glucosidase inhibitors and thiazolidinediones.
Each of the current agents available for use in treatment of diabetes has certain disadvantages. Accordingly, there is a continuing interest in the identification and development of new agents, which can be orally administered, for use in the treatment of diabetes.
The thiazolidinedione class listed above has gained more widespread use in recent years for treatment of type II diabetes, exhibiting particular usefulness as insulin sensitizers to combat “insulin resistance”, a condition in which the patient becomes less responsive to the effects of insulin. There is a continuing need for nontoxic, more widely effective insulin sensitizers.
Recent advances in scientific understanding of the mediators involved in acute and chronic inflammatory diseases and cancer have led to new strategies in the search for effective therapeutics. Traditional approaches include direct target intervention such as the use of specific antibodies, receptor antagonists, or enzyme inhibitors. Recent breakthroughs in the elucidation of regulatory mechanisms involved in the transcription and translation of a variety of mediators have led to increased interest in therapeutic approaches directed at the level of gene transcription.
As indicated above, the present invention is also concerned with treatment of immunological diseases or inflammation, notably such diseases as are mediated by cytokines or cyclooxygenase. The principal elements of the immune system are macrophages or antigen-presenting cells, T cells and B cells. The role of other immune cells such as NK cells, basophils, mast cells and dendritic cells are known, but their role in primary immunologic disorders is uncertain. Macrophages are important mediators of both inflammation and providing the necessary “help” for T cell stimulation and proliferation. Most importantly macrophages make IL-1, IL-12 and TNF-α all of which are potent pro-inflammatory molecules and also provide help for T cells. In addition, activation of macrophages results in the induction of enzymes, such as cyclooxygenase II (COX-2), inducible nitric oxide synthase (iNOS) and production of free radicals capable of damaging normal cells. Many factors activate macrophages, including bacterial products, superantigens and interferon gamma (IFNγ). It is believed that phosphotyrosine kinases (PTKs) and other undefined cellular kinases are involved in the activation process.
Cytokines are molecules secreted by immune cells that are important in mediating immune responses. Cytokine production may lead to the secretion of other cytokines, altered cellular function, cell division or differentiation. Inflammation is the body's normal response to injury or infection. However, in inflammatory diseases such as rheumatoid arthritis, pathologic inflammatory processes can lead to morbidity and mortality. The cytokine tumor necrosis factor-alpha (TNF-α) plays a central role in the inflammatory response and has been targeted as a point of intervention in inflammatory disease. TNF-α is a polypeptide hormone released by activated macrophages and other cells. At low concentrations, TNF-α participates in the protective inflammatory response by activating leukocytes and promoting their migration to extravascular sites of inflammation (Moser et al., J Clin Invest, 83:444–55, 1989). At higher concentrations, TNF-α can act as a potent pyrogen and induce the production of other pro-inflammatory cytokines (Haworth et al., Eur J Immunol, 21:2575–79, 1991; Brennan et al., Lancet, 2:244–7, 1989). TNF-α also stimulates the synthesis of acute-phase proteins. In rheumatoid arthritis, a chronic and progressive inflammatory disease affecting about 1% of the adult U.S. population, TNF-α mediates the cytokine cascade that leads to joint damage and destruction (Arend et al., Arthritis Rheum, 38:151–60, 1995). Inhibitors of TNF-α, including soluble TNF receptors (etanercept) (Goldenberg, Clin Ther, 21:75–87, 1999) and anti-TNF-α antibody (infliximab) (Luong et al., Ann Pharmacother, 34:743–60, 2000), have recently been approved by the U.S. Food and Drug Administration (FDA) as agents for the treatment of rheumatoid arthritis.
Elevated levels of TNF-α have also been implicated in many other disorders and disease conditions, including cachexia, septic shock syndrome, osteoarthritis, inflammatory bowel disease such as Crohn's disease and ulcerative colitis etc.
It can be seen that inhibitors of TNF-α are potentially useful in the treatment of a wide variety of diseases. Compounds that inhibit TNF-α have been described in several patents.
Excessive production of IL-6 is implicated in several disease states, it is highly desirable to develop compounds that inhibit IL-6 secretion. Compounds that inhibit IL-6 have been described in U.S. Pat. Nos. 6,004,813; 5,527,546 and 5,166,137.
The cytokine IL-1β also participates in the inflammatory response. It stimulates thymocyte proliferation, fibroblast growth factor activity, and the release of prostaglandin from synovial cells.
Elevated or unregulated levels of the cytokine IL-1β have been associated with a number of inflammatory diseases and other disease states, including but not limited to adult respiratory distress syndrome, allergy, Alzheimer's disease etc. Since overproduction of IL-1β is associated with numerous disease conditions, it is desirable to develop compounds that inhibit the production or activity of IL-1β.
It will be appreciated from the foregoing facts that, while there have been extensive prior efforts to provide compounds for inhibiting, for example, TNF-α, IL-1, IL-6, COX-2 or other agents considered responsible for immune response, inflammation or inflammatory diseases, e.g. arthritis, there still remains a need for new and improved compounds for effectively treating or inhibiting such diseases.
With an objective of providing compounds, which are effective for such treatments as well as for the treatment of, for example, insulin resistance, hyperlipidemia, obesity, inflammation, multiple sclerosis and arthritis, we have continued our research to develop new thiazoldinediones.
An objective of the present invention is to provide novel dipeptide phenyl ether compounds, their derivatives, their analogs, their tautomeric forms, their stereoisomers, their polymorphs, their pharmaceutically acceptable salts, their pharmaceutically acceptable solvates and pharmaceutical compositions containing them or their mixtures that are useful for treatment of disorders associated with insulin resistance, such as polycystic ovary syndrome, as well as hyperlipidemia, coronary artery disease and peripheral vascular disease, and for the treatment of inflammation and immunological diseases, particularly those mediated by cytokines such as TNF-α, IL-1, IL-6, IL-1β and cyclooxygenase such as COX-2.
Another objective of the present invention is to provide novel dipeptide phenyl ether compounds, their derivatives, their analogs, their tautomeric forms, their stereoisomers, their polymorphs, their pharmaceutically acceptable salts, their pharmaceutically acceptable solvates and pharmaceutical compositions containing them or their mixtures having enhanced activities, with little or no toxic effect.
Yet another objective of the present invention is to provide a process for the preparation of novel dipeptide phenyl ether compounds of formula (I), their derivatives, their analogs, their tautomeric forms, their stereoisomers, their polymorphs, their pharmaceutically acceptable salts and their pharmaceutically acceptable solvates.